Whitening Trays, Endo Accesses, and Stone Models – Oh My!

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Whitening Tray with Stone Model

We are wrapping up yet another month in the SIM clinic. That means that I have more pictures and projects to share. It is amazing just how quickly time flies in dental school!

Over the last couple of weeks we partnered up to create whitening trays for each other. This required us to take impressions of our partner’s mouth and cast stone models as well. We also did endodontic accesses on real teeth for the first time which was nice–one maxillary and the other mandibular.

Taking Impressions

Before making whitening trays you have to take an impression of your patient’s mouth. Our class spent about an hour in the clinic taking turns making impressions on each other. We had plenty of faculty around to help out when we made our first imperfect impressions. By the end most of us got the hang of it.

The alginate impressions we took are called negative impressions because we use them to create a stone model replica of our patient’s mouth. Our next step was to take our impressions back to the SIM clinic where we could pour our stone models into the alginate impressions we made.

Stone Models

It can be tricky to work with stone. It tends to trap air and form bubbles when poured. You have to pour slowly and spread the material over all occlusal and incisal surfaces thinly. Working with a vibrating plate helps ensure that there are as few bubbles as possible. Bubbles are bad!

I didn’t manage to take any pictures of myself pouring the stone because it’s a messy process and also the space was crowded. I didn’t want to take up too much time when people were waiting to use the vacuum mixers and vibrating plates.

After the stone model has dried we take it over to the grinder. I did manage to snap a photo there:

Stone Model and Grinder

Next, I took the stone arch back to my bench and ground down some of the excess material that I couldn’t get with the big grinding wheel in the lab.

Stone Model and Hand Grinder

Once you have the arches the way you want them, it is time to pour up the bases and set the arches in the stone base formers. Unfortunately, I let the mandibular arch sink too far into the stone base. You can see it on the right side of the image below. The good news though is that I managed to avoid creating many bubbles in the cast.

You can see what the finished product looked like below:

Finished Stone Models

Not perfect, but not bad

There are lots of bubbles in the base, and a few in the palate. But these are less of an issue than bubbles in the teeth. The important thing is that bubbles won’t prevent you from making accurate whitening trays.

Also, you may have noticed that there is some excess material on the front of the mandibular arch at the gum line. That is an artifact from the Alginate impression I took. Because it did not occur at the level of the teeth it doesn’t matter for making the whitening trays. In the future I will try to avoid such artifacts, but this is a learning process.

Whitening Trays

In order to make the stone models fit into the tray maker, I had to thin the base out to about a half inch thick. Now we place the stone model cast into our whitening tray maker and this is the result:

Whitening Tray with Stone Model

Next we cut the stone model out of the plastic which gives us the beginnings of our whitening tray:

Whitening Tray Unfinished Whitening Tray Unfinished

Finally we cut the whitening tray out using a couple of different pairs of scissors. You want to scallop the edges on the facial / buccal side. This helps to prevent the whitening agent from contacting soft tissue.

Whitening Trays Finished And there you have it! Two finished whitening trays. Hopefully my partner liked them…

Endodontic Accesses and IRM Fillings

Midwestern starts us early with indirect vision which is a good thing. It is difficult and often frustrating to work upside down and backwards in a tiny mirror covered with water droplets. Starting early gives us a lot of time to practice and then master indirect vision.

This week we had to complete two endodontic accesses. Both teeth were natural teeth, one was a maxillary molar and the other was a mandibular molar. On the mandibular molar (I had #19) we had to perform an endo access, complete an IRM (Intermediate Restorative Material) filling, remove the IRM and then fill the tooth with composite. On the maxillary tooth we just had to do the endo access and then fill it.

I didn’t get very many images of this process unfortunately, and all but one of them was blurry. But here is a photo I took of my mandibular prep after removing the IRM (a bit blurry, sorry):

Endodontic Access #19

In hindsight I could have been more conservative with my endo access. This is only my first endo access on a molar. But I think that angling the bur would have allowed me to retain more tooth structure on the occlusal surface while still gaining access to all of the roots in the tooth. In the future I will try to take that approach.

This is how #19 looked after I finished my class I restoration:

Class 1 Restoration #19

Class 1 Restoration #19

Restorations on natural teeth are much easier than Ivorine teeth in my opinion. I think that most of my classmates would agree. They are much more forgiving for one. I am pretty happy with the restoration I did on the tooth above. The surface looks a bit rough because it still has some debris on it and wasn’t yet polished. Also, the anatomy was a bit tricky, but I think it turned out really well.

To Be Continued…

The quarter is not yet finished, and we have a lot more ahead. We are supposed to expand our basic restorative repertoire to include Class II, III, IV, and V before finishing our first year. I missed last week due to an ASDA event in Washington D.C. that I will write about shortly.

Next week we are going to be performing teeth cleaning on our partners. Luckily for me, my partner was a hygienist before starting dental school. She is definitely getting the short end of the deal with me!

I am extremely satisfied with the clinical education we have received so far at Midwestern. I have had a chance to speak with students at schools all across the nation through ASDA and over the internet. It is truly remarkable just how much clinical training we receive at this school in comparison to others.

I plan to share more SIM clinic projects by the end of the year. It is sometimes hard for me to keep up with school work, this website, and all of my other commitments, so bear with me!

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